adds debugging to dnsserver (#1046)

libraries/DNSServer/src/DNSServer.cpp

@@ -2,6 +2,12 @@
 #include <lwip/def.h>
 #include <Arduino.h>
 
+// #define DEBUG_ESP_DNS
+#ifdef DEBUG_ESP_PORT
+#define DEBUG_OUTPUT DEBUG_ESP_PORT
+#else
+#define DEBUG_OUTPUT Serial
+#endif
 
 DNSServer::DNSServer()
 {
@@ -184,6 +190,11 @@ void DNSServer::replyWithIP()
   _udp.write((unsigned char*) &answerIPv4, 2 );
   _udp.write(_resolvedIP, sizeof(_resolvedIP)); // The IP address to return
   _udp.endPacket();
+
+  #ifdef DEBUG_ESP_DNS
+    DEBUG_OUTPUT.printf("DNS responds: %s for %s\n",
+            IPAddress(_resolvedIP).toString().c_str(), getDomainNameWithoutWwwPrefix().c_str() );
+  #endif  
 }
 
 void DNSServer::replyWithCustomCode()